1. Field of the Invention
The present invention relates to an apparatus and method for displaying stereoscopic images without having to wear stereoscopic spectacles.
2. Description of the Prior Art
FIG. 13 is a schematic view depicting a prior art display of stereoscopic images using stereoscopic glasses 30. The apparatus works by alternating, at high frequency, the display of images for the left eye 5 and images for the right eye 4. Moreover, a polarizing filter 33 having a high-speed liquid-crystal shutter that is in contact with a display screen 34 is used to give the displayed images mutually orthogonal polarization planes. By wearing the stereoscopic glasses 30, which are selectively polarizing, the left and right eyes 5 and 4 of a viewer 3 viewing the images can see these images independently. By means of these properties, stereoscopic pictures can be displayed by exhibiting parallactic images. When distant scenery is displayed using this picture display apparatus 35, the focal point of the eyes of the viewer 3 is on the display screen. Also when close scenery is displayed, the focal point of the eyes of the viewer 3 is on the display screen, giving rise to a discrepancy between the viewer""s parallax and the focal point. The arrow 31 in FIG. 13 indicates the distance corresponding to the parallax at the point within a display area 36 at which the displayed image is at its closest, and. arrow 32 shows the difference between the image position corresponding to the parallax and the position corresponding to the focal point of the eyes. The magnitude of this difference is the discrepancy that arises between the parallax and focal point of the viewer 3.
Stereoscopic displays that do not require the wearing of stereoscopic glasses include the type which reproduce light produced by an object, and the type comprising an arrangement that presents respective images to each eye. The former includes holograms and volume displays. A problem with these is that they need a mechanism for processing large amounts of image data and complex devices for displaying the data. Such requirements pose difficulties when it comes to applications involving real-time display of high-resolution images and moving pictures. On the other hand, the latter type includes methods involving the use of lenticular lenses, image separators, and selective-emission backlighting and the like.
In the case of stereoscopic displays that show binocular parallactic images, with respect to an arbitrary viewpoint, interaction with the stereoscopic images requires coincidence between the coordinate systems of the visual information and the coordinate systems of the physical information. This is achieved by measuring the positions of the viewer""s eyes in three dimensions and displaying the images matched to the viewpoints. However, as in the case of using the apparatus of FIG. 13, with this method, there is a problem in that, since the focal point of the viewer""s eyes is on the display surface, it is difficult to get the stereoscopic image to jump out very far from the display apparatus. The reason for this is physiological: with respect to the perception of an object near to the eye, focal point information is given the same importance as parallax. Because of this, if an image with too much parallax is used in an effort to display an image in front of a viewer, the viewer becomes unable to perceive it as a stereoscopic image owing to excessive visual fatigue or dizziness. Furthermore, in applications in which the viewer uses part of his body in an interactive task, because it is necessary to present the stereoscopic image at a close distance and it is also necessary for the display apparatus to be arranged so that it does not physically obstruct movements of the viewer, the problem cannot be resolved by bringing the display apparatus closer. Thus, it has not been possible to fully use prior art stereoscopic displays utilizing binocular parallax for such applications.
In the stereoscopic image display apparatus of the present invention, an image-separation apparatus and image-formation system are disposed between the display apparatus and the viewer. The disclosure of JP-A-HEI 8-307907 is an example of a prior art arrangement of a projection type stereoscopic image display apparatus having a configuration similar to that of the present invention. The apparatus of the disclosure comprises image display means whereby image light for the left and right eyes having mutually different angles of polarization is projected onto a diffuser panel to display on the diffuser panel images for each eye; light path selection means for selecting light paths whereby image light based on the images for the left eye and image light based on the images for the right eye displayed by the image display means are transmitted by respective areas so as not to be superposed on a two-dimensional plane; polarization angle displacement means that imparts the same polarization angle to the image light for the left and right eyes either before or after the light has been transmitted by the areas; a light converging system for focusing on left and right eye positions the light having the same polarization angle thus transmitted by the respective areas; side-of-face detection means for detecting the left and right eye positions; and transmission area control means that, based on the side-of-face detection result, controls the areas that transmit the image light for the right and left eyes. The object of the projection type stereoscopic image display apparatus is just to present images to both eyes without using stereoscopic glasses. Although it has an apparatus for identifying the sides of the face for the purpose of dividing the light, it does not have a system for three-dimensional measurement of the positions of the two eyes.
Because it does not have an arrangement for changing images according to the position of the viewpoint and cannot therefore accurately ascertain the three-dimensional position of a stereoscopic image, the above apparatus cannot be used for interactions between the viewer and the stereoscopic image. In addition, the apparatus uses an optical system whereby the real image display plane is generated between the viewer and the lenses, giving rise to problems such as that the real image plane is distorted depending on the three-dimensional position of the observation point and that the three-dimensional position of the eyes cannot be identified. These are problems that cannot be resolved. Thus, in addition to the usual sense of discomfort caused by three-dimensional displays that do not refresh the images in accordance with the position of the viewpoint, there is also the discomfort produced by the distortion of the real image plane distorting the screen being viewed.
In the present invention, real images are formed between the viewer and the coupling system or converging system, and the images shown on the display apparatus are corrected by information on the position of the viewer""s eyes. This is where the present invention differs from that of the above disclosure. The problem with prior art stereoscopic display methods and apparatuses that do not require the wearing of stereoscopic glasses is that the type which reproduces light produced by an object needs a mechanism for processing large amounts of image data and complex devices for displaying the data, while with the type that presents respective images to each eye, it is difficult to impart a perception of the stereoscopic image coming out in closeup from the screen.
In view of the above problems, an object of the present invention is to provide an apparatus and method for displaying a stereoscopic image in front of a viewer that appears to have depth, without the viewer wearing stereoscopic glasses.
Another object of the invention is to provide a small, light apparatus for displaying stereoscopic images that can be readily moved.
A further object of the invention is to provide an apparatus and method for displaying a stereoscopic image that expands the extent within which the viewer can move while still viewing the stereoscopic image.
In accordance with the present invention, the above objects are attained by a stereoscopic image display apparatus comprising at least one display apparatus that displays first and second images having parallax; an image-separation apparatus that separates the first and second images from the display apparatus; an image formation system that forms the first and second images thus separated on respective eyes; and a position detection means able to acquire information on positions of eyeballs of a viewer; wherein the image-separation apparatus is arranged between the display apparatus and the image formation system on a light path on which light information emitted by the display apparatus reaches the viewer, the image formation system is positioned between the image-separation apparatus and the viewer, real images of the display apparatus are formed between the image formation system and the viewer, and display content of the first image and display content of the second image are changed in accordance with the information on the positions of the viewer""s eyeballs.
The present invention also comprises the above stereoscopic image display apparatus in which the at least one display apparatus has a configuration comprising a first projector for displaying an image having first characteristics and a second projector for displaying an image having second characteristics that differ from those of the first image.
The present invention also comprises the above stereoscopic image display apparatus in which the at least one display apparatus is a display apparatus that alternately displays first images at a first display frequency and second images at a second display frequency that is substantially the same as the first display frequency.
The present invention also provides a stereoscopic image display apparatus that in addition to the above configuration has a configuration in which the image-separation apparatus selects a light path in conjunction with viewer eyeball movement.
The present invention also provides a stereoscopic image display apparatus that in addition to the above configuration has a configuration that includes a plurality of display apparatuses and a plurality of real image planes formed by real images of the display apparatuses formed between the image formation system and the viewer; means for selecting one or a combination of display apparatuses from among the plurality of display apparatuses in accordance with image perspective information; and means for displaying images on the selected one or combination of the display apparatuses.
The present invention also comprises a stereoscopic image display apparatus having a light converging system between the at least one display apparatus and the image-separation apparatus.
The above objects are also attained by a stereoscopic image display method comprising steps of displaying on a display apparatus a first or second image corrected according to positional coordinates of a viewer""s right or left eye, transmitting light signals emitted by the display apparatus through an image-separation apparatus that separates the first and second images, guiding the transmitted light signals to an image formation system, forming real images of the display apparatus between the image formation apparatus and the viewer, and presenting the formed images to the viewer.
The above objects are also attained by a stereoscopic image display method that in addition to the above steps, includes a step of modifying images on the display apparatus in accordance with movement in a viewer eye position, wherein, in an image creation method, with respect to all pixels xeX included in a set X of pixels of a three-dimensional image to be displayed, images presented to a viewer""s right eye are drawn at points at which light paths that include line segments x-er connecting x and a three-dimensional position er of the right eye intersect a display plane of the display apparatus, and images presented to a viewer""s left eye are drawn at points at which light paths that includes line segments x-el connecting x and a three-dimensional position el of the left eye intersect the display plane of the display apparatus.
The stereoscopic image display method of the present invention also includes a step of transmitting light signals produced by the display apparatus through the image-separation apparatus via a light converging system.
As described in the foregoing, a stereoscopic image can be displayed that appears to a viewer to be a solid image in front of the viewer by utilizing information on the positions of the viewer""s eyes. Moreover, even if the viewer moves, since the light path used is selected in conjunction with the movements of the viewer""s eyeball position, the viewer can continue to see the stereoscopic image. Furthermore, since the light converging system is positioned between the display apparatus and the image-separation apparatus, the apparatus can be made small and light.
The above and other objects, further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and following detailed description of the invention.